Telephone switch apparatus.



H. P. GLAUSEN. TELEPHONE SWITCHBOARD APPARATUS.

APPLICATION FILED NOV. 21. 1903.

PATENTED JULY 30, 1907,.

" :II IIMII I UNITED STATES PATENT OFFICE.

HENRY P. CLAUSEN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE AMERICANELECTRIC TELEPHONE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATIONTELEPHONE SWITCHBOARD APPARATUS.

Specification of Letters Patent.

Patented July 30, 1907.

Application filed November 21,1903. Serial No. 182,075.

To all whom it may concern:

Be it known that I, HENRY P. OLAUSEN, a citizen of the United States ofAmerica, and a resident of Chi cago, Cook county, Illinois, haveinvented a certain new and useful Improvement in Telephone Switch boardApparatus, of which the following is a specification.

It is a matter of common knowledge, that in telephone systems, or atleast in some systems, that when two subscribers are talking, thetesting of either line by the operator at the central station, inresponse to a call sent in by a third party for connection with one ofthese lines, is liable to produce derived circuits of such character asto enable this third party to overhear the conversation being carried011 between the two subscribers ah'eady connected up, and, in addition,to produce noise or undesirable disturbances on one or more of thelines, and perhaps on all three lines. It is for the purpose ofovercoming this difiiculty, and of providing a multiple switchboardapparatus which will enable the operators to make the-busy-test in theusual mannerthat is to say, to touch the tip of the calling plug to thering or test-thimble of the multiple jack connected with the called-forsubscribers line-without any danger or liability of the conversationbeing carried on over the tested line being heard by the third party, orparty in whose behalf the operator has made the test, and without dangerof producing annoying disturbances or sounds on any of the lines, thatmy improved impedance arrangement is employed in the manner shown anddescribed.

In its preferred form, my invention comprises an op erators cord-circuitin which two corresponding contacts of the answering and calling plugs,preferably the tip contacts, are connected through the medium of animpedance coil which is normally short-circuited by the operatorslistening key, but which becomes the only available path for thetransmission of current between the corresponding contacts of the twoplugs when the operator presses the listening key, as, for example, inmaking the usual and Well-known busy-testthat is to say, the busy-testwhich consists in pressing the listening key and touching the tip of thecalling plug to the ring or test-thimble of the multiple jack connectedwith the called-for subscribers linethe operator, in such case, hearingnothing if the line is not in use, or, on the other hand, receiving adistinct click or sound in her receiver, if the line is in use. Thus,with the foregoing provision, it is readily apparent that an' operatorcan make the busy-test in the usual and approved manner without anyliability of whatever conversation is being carried on over the testedline'being heard by the third party or calling subscriber, and, owing tothe retarding effect which the impedance coil has on initial flow ofcalling current without producing scribers lines; for in thus making thetest, the operator opens up the short-circuit which normally extendsaround the said impedance coil, thereby permitting a suflicient flow ofbattery current through the cord-circuit to give the test-signal, if aline is'busy, but, owing to the presence of the impedance coil in thecircuit, preventing a flow of voice currents through the cordcircuit tothe calling subscribers line, and also preventing the quick flow or rushof battery current which, by producing discharges from whatevercondensers are employed, usually tends to produce unpleasant sounds inthe subscribers receivers; it being understood, of course, that beforethus testing the called-for subscribers line the operator has alreadyinserted the answeringplug in the jack connected with the callingsubscribers line; and it is the necessity of thus connecting the cordcircuit with the calling-subscribers line before making which givesutility to my invention by enabling my improved impedance coilarrangement to preclude all possibility of the conversation between twoconnected subscribers being overheard by any other subscriber in whosebehalf the operator may test one of the two connected lines, and byenabling the operator to make what may betermed a quiet busytest.

The nature and advantages of my invention will, however, hereinaftermore fully appear.

The accompanying drawing is a diagram illustrating a common batterymultiple switchboard telephone system, embodying the principles of myinvention.

The substation apparatus shown at the substations A, B and C, can. be ofany suitable known or approved character. These subscribers orsubstation telephone sets are connected with the exchange or centralstation through the medium of the line-wires a, b and c, in any suitableor desired manner. As the exchange is of the common battery andmultiple-switchboard type, the current for both signaling and talkingpurposes is supplied to the subscribers lines from a common battery D.Each subscribers line is provided, at the central station, with bothanswering and multiple-jacks. For example, the line a can be providedwith an answeringjack a, and, on the other sections of the switchboard,with multiple-jacks a and a In a similar way, the line I) can bearranged to terminate in the answeringjacks Z) and the multiple jacks band If. The line c can terminate in similar jacks 0 c and o Theline-signal apparatusthat is to say, the devices by which thesubscribers attract the attention of the operatorscan be of any suitableknown or approved character. In the diagram, E represents line-signalapparatus for the line a, while the line-signal apparatus I described.It will be understood, however, that the.

cut-off relays of the line do not operate when the subscribers take downtheir receivers, as the said relays are suitably adjusted to preventthis. So also in respect to the operators cord circuits, forestablishing and disestablishing connection between the differentsubscribers lines. These operators cord-circuits H and I located infront of different operators, can be of any suitable known or approvedcharacter. The cord-circuit H can be provided with answering and callingplugs h and h, with suitable supervisory apparatus 71?, and with theusual operators talking set Ir, consisting of a transmitter and areceiver. The cord-circuit is, of course, also provided in the usual andwell-known manner, with ringing and listening keys h", h'. The featureof this cord-circuit which constitutes my invention, consists in theprovision. of an impedance element, such, for example, as the impedancecoil h connected normally in parallel with the spring of the listeningkey h", whereby it is normally short-circuited. But when this key ispressed, it will be seen that the spring leaves the contact h therebyremoving this short-circuit from around the impedance-coil, thus leavingthe said coil to constitute a portion of the conducting path between thetip contacts of the two plugs. In this way, the impedance coil providesa suitable path for the battery current necessary in making the test,but at the same time precludes the passage of voice currents over thetested line to the line of the waiting subscriber. For example, as shownin the diagram, the cord-circuit I has both its plugs inserted in thejacks of the lines a and b, the subscribers at A and B thereby beingconnectcd up for conversation. As illustrated, the subscriber O issupposed to be calling [or subscriber A, and the operator provided withthe cord-circuit H is sup posed to' be making the usual busy-test. Suchbeing the case, the answering-plug h has been inserted in theanswering-jack connected with the line 0, and the operator is touchingthe tip of the plug h to the ring or testing thimble of themultiple-jack a", which latter is connected with the line a. At the sametime, the operator presses the listening key h, thereby removing theshortcircuit which normally extends around the impedance coil h. Thisleaves the test-circuit intactthat is to say, leaves a path for batterycurrent to flow over the ring of the jack a, through. the tip of: theplug h, thence through the impedance coil If and the listening-key h,thence through the operators receiver and back to the other pole ol thebattery, as shown. This gives the click or sound in the operatorsreceiver, necessary in order to give the busy signal, and advise herthat the called-for subscribers line is busy; but, at the same time, itwill be seen that the tested circuit thus formed includes the impedancecoil, and consequently that while battery current can thus flow over thecircuit, no voice currents can traverse the circuit. In this way, thecord-circuit normally presents two parallel strands or conducting paths,whereby any two subscribers can be connected up. When the operatorpresses the listening-key, however, as in making a test, then theimpedance-coil is introduced into one side of the cord-circuit, therebyprecluding the possibility of any voicecurrents traversing thecord-circuit from a busy calledfor subscribers line to the line of thecalling subscriber.

It will be readily understood that the resistance of the impedance-coil,as well as other devices in the system, can be adjusted or regulated tosuit circumstances or conditions, and in accordance with therequirements'of diiierent systems. As previously stated, the impedancecoil is of further utility, in this: It pre vents a quick rush ofbattery current through the circuit, thus preventing such a charging ofthe condenser or condensers as would be likely, when the condensersdischarge, to produce unpleasant sounds or disturbances in any of thesubscribers lines.

What I claim as my invention is:

i 1. A centratenergy multiple switchboard telephone system, providedwith operators cord-circuits having normally short-circuitedimpedance-coils, together with spring jacks adapted to be connected withthe cord-circuits in the establishment of connection betweendilferentsubscribers, each spring jack having an outer contact constituting apart of both the talking and busy test circuits.

2. A central-energy multiple switchboard telephone system provided withoperators cord-circuits having the usual or suitable listening keys, andhaving also impedance elements normally short-circuited by said keys,together with spring jacks adapted to be connected with thecord-circuits in the establishment of connection between differentsubscribers, each spring jack having an outer contact constituting apart of both the talking and busy test circuits.

A central-energy multiple switchboard telephone system, provided withoperators cord-circuits equipped for making the usual busy-test, andhaving also normally short-circuited impedance elements adapted, in eachcase, to be brought into one side of the cord circuit when the operatormakes a busy-test, together with spring jacks adapted to be connectedwith the cord-circuits in the establishment of connection betweendifferent subscribers, each spring jack having an outer contactconstitutinga part of both the talking and busy test circuits.

4. A central-energy multiple switchboard telephone system, provided withoperators cord-circuit apparatus having suitable connections for formingthe test circuits, and pro vided also with normally short-circuitedimpedance-coils adapted to constitute part of said test circuits,together with spring jacks adapted to be connected with the cordcircuitsin the establishment of connection between different subscribers, eachspring jack having an outer contact constituting a part of both thetalking and busy test circuits.

5. A common battery multiple telephone exchange system, having operatorscord-connecting apparatus adapted to provide derived testing circuits,and impedance-coils adapted to constitute part of said test circuits,together with spring jacks adapted to be connected with the cordcircuitsin the establishment of connection between differ ent subscribers, eachspring jack having an outer contact constituting a part of both thetalking and busy test circuits together with normally closedlistening-key contacts normally shunting or short-circuiting said coils.

G. A common battery multiple switchboard telephone ex change systemhaving operators cord-circuits, one side of each cord-circuit beingprovided with a normally shortcircuited impedance-coil, and eachcord-circuit being pro vided with means for opening the short-circuitwhen the operator desires to make a busy-test, together with springjacks adapted to be connected with the cord-circuits in theestablishment of connection between different subscribers, each springjack having an outer contact constituting a part of both the talking andbusy test circuits.

Signed by me at Chicago, Cook county, Illinois, this 16th day ofNovember, 1903.

. HENRY P. CLAUSEN:

Witnesses:

S. B. CHABOWSKI, WM. A. HARonRs.

